1. Field of the Invention
The present invention relates to a development apparatus of a liquid electrophotographic printer, and also, to a method for controlling the mode of a developing station of a liquid electrophotographic printer, for preventing a photosensitive belt from being contaminated while cleaning the development roller and performing sufficient cleaning of the development roller and a development roller driving apparatus therefor.
2. Description of the Related Art
In general, a liquid electrophotographic printer such as a color laser printer, as shown in FIG. 1, includes a photosensitive belt 10 supported by a plurality of rollers 11, 12 and 13 installed in a printer body (not shown) which makes a circular movement in an endless track. An image to be printed is developed on one surface of the photosensitive belt 10 by a developing station 14, and the developed image is dried via a drying station 15 to then be transferred to a sheet of printing paper 1 by a transfer/pressing station 16 having a transfer roller 16a and a pressing roller 16b. The developing station 14 supplies a developer liquid to the photosensitive belt 10, and separates most of the liquid carrier contained in the developer liquid so that only toner is left over a latent electrostatic image portion of the photosensitive belt 10, thereby allowing transfer of the image in the transfer/pressing station 16.
The developing station 14, as shown in FIG. 3, is installed such that a development roller 21 and a development backup roller 22 selectively come in tight contact with the photosensitive belt 10 disposed therebetween. A developer liquid spray nozzle 23 is installed to spray a developer liquid between the development roller 21 and the photosensitive belt 10. The development roller 21 uniformly applies the developer liquid sprayed from the spray nozzle 23 to the photosensitive belt 10 while being rotated by a driving apparatus (not shown). A cleaning roller 24 is installed under the development roller 21 to be selectively in contact with the development roller, for cleaning the development roller 21. A squeezing roller 31 and a squeezing backup roller 32 are installed in the rear of the development roller 21 in view of the rotation direction of the development roller 21, so as to selectively come into tight contact with the photosensitive belt 10 disposed therebetween. By being passive-rotated in selective contact with the photosensitive belt 10, the squeezing roller 31 squeezes out the liquid carrier from the developer liquid applied on the photosensitive belt 10 for removal. Subsequently, the squeezing roller 31 reversely rotates in a drip line removal mode. Thus, although not shown, a separate driver for reversely rotating the squeezing roller 31 is provided in the developing station 14. A squeezing blade 34 contacts the squeezing roller 31 reversely rotating in the drip line removal mode, and removes the ink drawn by the squeezing roller 31. The squeezing blade 34 is configured to selectively contact the squeezing roller 31 and is spaced apart from the squeezing roller 31 in the printing mode, as shown in FIG. 3.
As shown in FIG. 4, the aforementioned developing station sequentially operates in the order of a printing mode (step S40), a development roller cleaning mode (step S50), a drip line removal mode (step S60) and a home mode (step S70), which will now be described in more detail.
Initially, in a printing standby state, the developing station is in a home mode (step S70). In the home mode (step S70), the development roller 21 and the squeezing roller 31 are spaced approximately 12 mm apart from the photosensitive belt 10. Here, the development roller 21 and the squeezing roller 31 do not rotate but are at a standstill.
In the home mode (step S70), if a printing start signal is applied, the development roller 21 and the squeezing roller 31 are pressed into tight contact with the photosensitive belt 10 by a pressing unit (not shown) with a predetermined pressure of about 20 kg/f. Here, the development roller 21 is rotated by a driver (not shown) and the squeezing roller 31 is passively rotated by the photosensitive belt 10. Then, a developer liquid is sprayed through the developer liquid spray nozzle 23, thereby performing the printing mode (step S40).
In the development roller cleaning mode (step S50), the development roller 21 is subjected to racing for the purposes of removing the developer liquid remaining on the developer liquid spray nozzle 23 and the cleaning roller 24 and sufficiently cleaning the development roller 21 after completing the printing mode (step S40). The development roller cleaning mode (step S50) is achieved by the racing of the development roller 21 in the same state as in the printing mode (step S40).
After completing the development roller cleaning mode (step S50), a drip line removal mode (step S60), in which unnecessary toner remaining on the photosensitive belt 10 is removed, is performed. In the drip line removal mode (step S60), the development roller 21 is spaced approximately 4 mm apart from the photosensitive belt 10. The squeezing roller 31 receives power from the not-shown driver in a state that it is pressed into tight contact with the photosensitive belt 10 with a predetermined pressure (about 4 kg/f), and rotates in the reverse direction to the printing mode, to collect the toner present on the photosensitive belt 10. Here, the squeezing blade 34 is brought into contact with the squeezing roller 31 which reversely rotates as above, and removes the toner collected by the squeezing roller 31.
After the drip line removal mode (step S60) is completed, the procedure is returned to the home mode (step S70) in which the development roller 21 and the squeezing roller 31 are spaced approximately 12 mm apart from the photosensitive belt 10 and is in a printing standby state.
However, according to the conventional method for controlling the mode of a developing station, a development roller cleaning mode is performed in a state that a development roller comes into tight contact with the photosensitive belt, after the printing mode and before the drip line removal mode. Thus, the photosensitive belt may be contaminated by the development roller while the development roller is being cleaned. Also, for the same reason as above, the development roller can be cleaned for only about 20 seconds. That is, a sufficient time for cleaning the development roller cannot be ensured. Accordingly, degradation in development quality cannot be avoided due to contamination of the development roller.
To solve the above problems, it is a first object of the present invention to provide a method for controlling the mode of a developing station of a liquid electrophotographic printer, which can prevent the photosensitive belt from being contaminated by a development roller in the development roller cleaning mode.
It is a second object of the present invention to provide a method for controlling the mode of a developing station of a liquid electrophotographic printer, which can ensure a sufficient time for cleaning the development roller.
It is a third object of the present invention to provide a development roller driving apparatus for implementing the method for controlling the mode of a developing station of a liquid electrophotographic printer.
Accordingly, to achieve the above objects, there is provided a method for controlling the mode of a developing station of a liquid electrophotographic printer, wherein a printing mode, a drip line removal mode and a home mode are sequentially performed, and a development roller is subjected to racing in the home mode to be cleaned.
Since the development roller is cleaned in the home mode in which the development roller is spaced approximately 12 mm apart from the photosensitive belt, the photosensitive belt is never contaminated by the development roller. Also, since cleaning of the development roller is performed after the drip line removal mode, a sufficient time for cleaning the development roller can be ensured.
According to another aspect of the present invention, there is provided a development roller driving apparatus for rotating a development roller which is positioned at different positions relative to a photosensitive belt according to a printing mode, a drip line removal mode, or the home mode. The apparatus includes a motor, which is a driving power source, a reduction gear train for reducing and transmitting power of the motor, a power relay gear installed to be engaged with the reduction gear train, and a link/gear assembly for transmitting the power relayed by the power relay gear to the development roller gear.
Here, the reduction gear train may include a first reduction gear having a large-diameter gear engaged with a pinion mounted on the motor shaft and a small-diameter gear coaxially installed with respect to the large-diameter gear of the first reduction gear, and a second reduction gear having a large-diameter gear engaged with the small-diameter gear of the first reduction gear and a small-diameter gear coaxially installed with respect to the large-diameter gear of the second reduction gear.
Also, the link/gear assembly may include a first gear installed to be engaged with the power relay gear, a link installed on a shaft of the first gear to be capable of swinging around the shaft and having a slot formed at one side into which the shaft of the second reduction gear is inserted, a second gear installed at one end of the link to be engaged with the first gear and the development roller gear, and an elastic supporting pin inserted into the shaft of the first gear, for elastically supporting the link counterclockwise to keep the second gear being engaged with the development roller gear.
In a preferred embodiment of the present invention, the development roller gear and the second gear engaged with the development roller gear have guiding surfaces provided at both ends of their teeth.